sched: Remove proliferation of wait_on_bit() action functions

The current "wait_on_bit" interface requires an 'action'
function to be provided which does the actual waiting.
There are over 20 such functions, many of them identical.
Most cases can be satisfied by one of just two functions, one
which uses io_schedule() and one which just uses schedule().

So:
 Rename wait_on_bit and        wait_on_bit_lock to
        wait_on_bit_action and wait_on_bit_lock_action
 to make it explicit that they need an action function.

 Introduce new wait_on_bit{,_lock} and wait_on_bit{,_lock}_io
 which are *not* given an action function but implicitly use
 a standard one.
 The decision to error-out if a signal is pending is now made
 based on the 'mode' argument rather than being encoded in the action
 function.

 All instances of the old wait_on_bit and wait_on_bit_lock which
 can use the new version have been changed accordingly and their
 action functions have been discarded.
 wait_on_bit{_lock} does not return any specific error code in the
 event of a signal so the caller must check for non-zero and
 interpolate their own error code as appropriate.

The wait_on_bit() call in __fscache_wait_on_invalidate() was
ambiguous as it specified TASK_UNINTERRUPTIBLE but used
fscache_wait_bit_interruptible as an action function.
David Howells confirms this should be uniformly
"uninterruptible"

The main remaining user of wait_on_bit{,_lock}_action is NFS
which needs to use a freezer-aware schedule() call.

A comment in fs/gfs2/glock.c notes that having multiple 'action'
functions is useful as they display differently in the 'wchan'
field of 'ps'. (and /proc/$PID/wchan).
As the new bit_wait{,_io} functions are tagged "__sched", they
will not show up at all, but something higher in the stack.  So
the distinction will still be visible, only with different
function names (gds2_glock_wait versus gfs2_glock_dq_wait in the
gfs2/glock.c case).

Since first version of this patch (against 3.15) two new action
functions appeared, on in NFS and one in CIFS.  CIFS also now
uses an action function that makes the same freezer aware
schedule call as NFS.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: David Howells <dhowells@redhat.com> (fscache, keys)
Acked-by: Steven Whitehouse <swhiteho@redhat.com> (gfs2)
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steve French <sfrench@samba.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140707051603.28027.72349.stgit@notabene.brown
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 7 insertions, 53 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index c355f73..770e167 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -856,27 +856,6 @@ void gfs2_holder_uninit(struct gfs2_holder *gh)
 }
 
 /**
- * gfs2_glock_holder_wait
- * @word: unused
- *
- * This function and gfs2_glock_demote_wait both show up in the WCHAN
- * field. Thus I've separated these otherwise identical functions in
- * order to be more informative to the user.
- */
-
-static int gfs2_glock_holder_wait(void *word)
-{
-        schedule();
-        return 0;
-}
-
-static int gfs2_glock_demote_wait(void *word)
-{
-	schedule();
-	return 0;
-}
-
-/**
  * gfs2_glock_wait - wait on a glock acquisition
  * @gh: the glock holder
  *
@@ -888,7 +867,7 @@ int gfs2_glock_wait(struct gfs2_holder *gh)
 	unsigned long time1 = jiffies;
 
 	might_sleep();
-	wait_on_bit(&gh->gh_iflags, HIF_WAIT, gfs2_glock_holder_wait, TASK_UNINTERRUPTIBLE);
+	wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE);
 	if (time_after(jiffies, time1 + HZ)) /* have we waited > a second? */
 		/* Lengthen the minimum hold time. */
 		gh->gh_gl->gl_hold_time = min(gh->gh_gl->gl_hold_time +
@@ -1128,7 +1107,7 @@ void gfs2_glock_dq_wait(struct gfs2_holder *gh)
 	struct gfs2_glock *gl = gh->gh_gl;
 	gfs2_glock_dq(gh);
 	might_sleep();
-	wait_on_bit(&gl->gl_flags, GLF_DEMOTE, gfs2_glock_demote_wait, TASK_UNINTERRUPTIBLE);
+	wait_on_bit(&gl->gl_flags, GLF_DEMOTE, TASK_UNINTERRUPTIBLE);
 }
 
 /**
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index 91f274d..992ca5b 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -936,12 +936,6 @@ fail:
 	return error;
 }
 
-static int dlm_recovery_wait(void *word)
-{
-	schedule();
-	return 0;
-}
-
 static int control_first_done(struct gfs2_sbd *sdp)
 {
 	struct lm_lockstruct *ls = &sdp->sd_lockstruct;
@@ -976,7 +970,7 @@ restart:
 		fs_info(sdp, "control_first_done wait gen %u\n", start_gen);
 
 		wait_on_bit(&ls->ls_recover_flags, DFL_DLM_RECOVERY,
-			    dlm_recovery_wait, TASK_UNINTERRUPTIBLE);
+			    TASK_UNINTERRUPTIBLE);
 		goto restart;
 	}
 
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index bc564c0..d3eae24 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1024,20 +1024,13 @@ void gfs2_lm_unmount(struct gfs2_sbd *sdp)
 		lm->lm_unmount(sdp);
 }
 
-static int gfs2_journalid_wait(void *word)
-{
-	if (signal_pending(current))
-		return -EINTR;
-	schedule();
-	return 0;
-}
-
 static int wait_on_journal(struct gfs2_sbd *sdp)
 {
 	if (sdp->sd_lockstruct.ls_ops->lm_mount == NULL)
 		return 0;
 
-	return wait_on_bit(&sdp->sd_flags, SDF_NOJOURNALID, gfs2_journalid_wait, TASK_INTERRUPTIBLE);
+	return wait_on_bit(&sdp->sd_flags, SDF_NOJOURNALID, TASK_INTERRUPTIBLE)
+		? -EINTR : 0;
 }
 
 void gfs2_online_uevent(struct gfs2_sbd *sdp)
diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c
index 94555d4..573bd3b 100644
--- a/fs/gfs2/recovery.c
+++ b/fs/gfs2/recovery.c
@@ -591,12 +591,6 @@ done:
 	wake_up_bit(&jd->jd_flags, JDF_RECOVERY);
 }
 
-static int gfs2_recovery_wait(void *word)
-{
-	schedule();
-	return 0;
-}
-
 int gfs2_recover_journal(struct gfs2_jdesc *jd, bool wait)
 {
 	int rv;
@@ -609,7 +603,7 @@ int gfs2_recover_journal(struct gfs2_jdesc *jd, bool wait)
 	BUG_ON(!rv);
 
 	if (wait)
-		wait_on_bit(&jd->jd_flags, JDF_RECOVERY, gfs2_recovery_wait,
+		wait_on_bit(&jd->jd_flags, JDF_RECOVERY,
 			    TASK_UNINTERRUPTIBLE);
 
 	return wait ? jd->jd_recover_error : 0;
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 1319b5c..2607ff1 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -864,12 +864,6 @@ static int gfs2_make_fs_ro(struct gfs2_sbd *sdp)
 	return error;
 }
 
-static int gfs2_umount_recovery_wait(void *word)
-{
-	schedule();
-	return 0;
-}
-
 /**
  * gfs2_put_super - Unmount the filesystem
  * @sb: The VFS superblock
@@ -894,7 +888,7 @@ restart:
 			continue;
 		spin_unlock(&sdp->sd_jindex_spin);
 		wait_on_bit(&jd->jd_flags, JDF_RECOVERY,
-			    gfs2_umount_recovery_wait, TASK_UNINTERRUPTIBLE);
+			    TASK_UNINTERRUPTIBLE);
 		goto restart;
 	}
 	spin_unlock(&sdp->sd_jindex_spin);